Variable pitch propeller



June 24, 1941; R. J. RUTHS ETAL VARIABLE PITCH PROPELLER' 2 sheets-sheet 1 Filed Axgg. 20, 1938 llllr l INVENTOR EOBEEI'J. fur-1 5 (/merLDonsm ATTORNEY June 24, 1941. R. J. RUTHS ETAL VARIABLE rrrca PROPELLER -Fi1ed Aug. 20, 1938 extending torsion shaft;

Patented June 24, 1941 VARIABLE, PITCH PBOPELLER Robert J. m... Baltimore, Mam nmyn Dodson, United States Navy Application August 20, 1938, Serial No. 225,890

(Granted under the act of March 3, 1883, as

' amended April 30, 1928; 370 O G. 757) 3 Claims.

This invention relates to variable pitch pro- 20 and is provided with a tapered bore 2| into I pellers and it has for its principal object the provision of anew and improved propeller o'r im-' peller for ships and pumps in which the pitch of "the several blades will be varied automatically in accordance with'the horsepower applied and the thrust exerted by the blade against a fluid environment. j

-With these and other objects in'view, as well as other advantages that may be incident to the use of the improvements, the invention consists in the parts and combinations thereof hereinafter set forth and claimed, with the understanding that the several necessary elements constituting the same may be varied in proportion and arrangement without departing from the nature and scope of the invention, as defined in the appended claims.

-In order to make the invention more clearly understood, there are shown in the accompanying drawinga'means for-"carrying the invention into practical use, without limiting the improvemen-ts in their useful application to the particular construction, which, for the purpose of explanation, have been made the subject of'illustration. V

In the accompanying drawings:

Fig. 1 is a longitudinal sectional view through .a propeller hub embodying the invention; Fig. 2 is aside elevational view with parts broken away of the structure shown in Fig. 1: Fig. 3 is a transverse sectional, view taken on line 3-3 of Fig. 2;

Fig. 4' is a longitudinal sectional view of a por-' tion of the propeller shaft showing the coaxially Fig. 5 is a transverse sectional line i5 of Fig. 4-; and

Figs. 6 and '7 are diagrammatic views showing the unbalanced construction of the leading and view. taken on trailing edges of the propeller blade and the change in pitch of the blade caused thereby.

Referring to thedrawings, a variable pitch propeller constructed according to the invention isshown as comprising a hub having a forward portion II and an after portion l2 secured together by longitudinally extending bolts i3 and provided with a scarfjoint'll therebetween to prevent relative rotation of the parts and to relieve the bolts l3 from shearing strains. A. hollow streamline hub cap I5 is secured to the, after portion H ofthe hub by means of a nipple l6 provided. on the former for screw threaded enwhich the rear end of the shaft 13a extends and is secured therein by a key 22.

The adjacent ends of the portions H and I! of the hub are recessed to form a central gear chamber 23 and their marginal edges are also.

formed with complementary semicircular recesses providing a plurality of circumferentially arranged sockets 24, herein shown as constitute ing three in number. These sockets each open into the gear chamber 23 and also into an inner rearwardly elongated channel 25 formed in the after portion l2 of the hub (Figs. 1 and 2). A plurality of propeller blades 26 are mounted on the hub l0 and theirroot portions are each formed with a neck 21 which is journalled in-the socket 24 and a collar disposed within the associated channel 25 for preventing radial displacement of the blade but permitting the blade to rotate about a radially extending axis}. The collars 28 are each formed with a segmental .bcvel gear 29 which meshes with a single bevel pinion 30 disposedwithin the chamber 23, thus insuring after to be described.

that the blades 26 willmove in uni on when roherein V tated about their axes- X, ina manner The pinion 30 is fixed to the rear endof 9. flexibletorsion or quill shaft 3| which extends forwardly through an axial bore 32 formed in the section Ha of the main drive shaft. The extreme forward end of the torsion shaft 3| is fixed to an external circular spline 33 (Fig. 5) which intergagement with the latter and isprevented from becoming unscrewed by a lock screw l1 threaded into both the portion l2 and cap IS in the 'plane I I of the hub is fixed to collar it formed on a sectionlira are main drlveshaft by means of bolts;

maximum and minimum pitches.

looks with an internal spline surface formed in a collar 34'. Cooperating with the collar 34'- is a second collar 34 which is preferably formed in two parts, as shown in Fig. 5, to permit it to be assembled on the shaft and is formed with an internal annular shoulder 35 (Fig. 4) for engage-- ment with an external circumferential grooveformed in the rear end of the section I341 of the. main drive, shaft. The halves of the collar 34 are secured by means of bolts 39'. to a collar 33,

which is fixed to the section Illa of the drive shaft by a key 31 and also to an annular. flange 33 formed on a forward section l3b of the drive shaft, thus tyingall of the parts together for rotationin unison, and anchoring the forward end of the torsion shaft 3| to-the main drive shaft.-

- The rotation of each of the blades 26 of the propeller and the torsion exertedtherebyupon the torsion shaft 3 l 'is prevented from exceeding a predetermined maximum limit which is determined by the pitch of maximum efllciency,-by means of a stop arm 40 (Fig. 2) which is pro.- vided on each of the collars 28, for abutting engagement with the side walls of the channel 25 within which such arm is located. I be secured to the sides of the stop arms to accurately limit the rotation or. the

Shims may blades within applied to the propeller.

OPERATION: Let it be assumed that the propeller is at rest and exerts no force against its surrounding fluid environment. Under such conditions the blades of the propeller occupy positions of maximum pitch, as is diagrammatically illustrated in Fig. 6. If power is now applied gradually to the drive shaft, the force reacting against the trailing edge TE of each blade, which is of greater surface area than the leading edge LE thereof, will cause 'the blade to turn about its axis X in a counterclockwise direction, decreasing its pitch and exerting a twisting strain upon the torsion shaft 3i; ing on the blades also aids in this forcing of the blades to a position of decreased pitch. As the horsepower is increased, this reactional force will correspondingly increase, and proportionally decrease the pitch of the blades until it reaches the pitch of maximum efficiency which will correspond to the horsepower of maximum efliciency When this point is reached, the stop arms 40 will engage the sides of the channels 25 and prevent any further turning movement of the blades and any further decrease in the strain transmitted to the torsion shaft 3|. Conversely, as the horsepower applied to the propeller by the prime mover is decreased, the energy stored in the torsion shaft 3| will rotate the blades 26 of the propeller in a reverse direction so as to correspondingly increase the pitch of the blades. Thus, it will be seen that the pitch of the blades of the propeller is at all times in accordance with the applied horsepower and at the most efficient pitch for such horsepower.

It will be understood that the above. description and accompanying drawings comprehend only e general and preferred embodiment of the invention and that various changes in construction, proportion and arrangement of the parts may be made within the scope of the appended claims without sacrificing any of the advantages of the invention.

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes. without the payment of thereon or therefor.

We claim:

1. A variable pitch propeller comprising a hub; a blade mounted on said hub for rotation about a radially extending axis, the trailing edge of said blade located on one side of said axis having a greater surface area than the leading edge thereany royalties of located on the opposite side of said axis, the

thrust exerted by the trailing edge of said blade thus tending to rotate said blade about said axis to decrease the pitch' thereof; a hollow main shaft having an after section on which said hub is mounted and a forward engine section, said after section having an annular groove formed in its forward end and said engine section having The centrifugal action actplacement of the-parts thereof; and gear means connecting the after end of said torsion shaft with said blade, whereby such rotational motion of said blade about said axis will transmit torsional strain to said torsion shaft and be opposed thereby, thus storing energy in said torsion shaft so as to rotate said blade in an opposite direction about said axis to increase the pitch of said blade with a decrease in the thrust exerted .thereby.

2. A variable pitch propeller comprising a hub; a blade mounted on said hub for rotation about a radially extending axis, the trailing edge of said blade located on one side of said axis having a greater surface area than the leading edge thereof located on the opposite side of said axis, the thrust exerted by the trailing edge of said blade thus tending to rotate said blade about said axis to decrease the pitch thereof; a hollow main shaft having an after section on which said hub a flange formed on its after end; a torsion shaft extending through the after section of said main shaft and having a splined portion formed on its forward end; a collar keyed to the forward.

end of the after section of said-main shaft; a split ring disposed in engagement with said groove; an internally splined anchor member disposed in locking engagement with the splined portion of said torsion shaft, through bolts passing through said flange, anchor member, split ring and collar and rigidly securing the assembly together to prevent relative axial and rotary disis mounted and a forward engine section, said after section having an annular groove formed in its forward end and said engine section having a flange formed on its after end; a torsion shaft extending through the after section of said main shaftand having a flange formed on it forward end; a collar keyed to the forward end of the after section of said main shaft; a split ring disposed in engagement with said groove; an anchor member disposed in looking engagement with the flange on said torsion shaft, means rigidly connecting said flanges, anchor member, split ring and collar to prevent relative axial and rotary displacement thereof; and gear means connecting the after end of said torsion shaft with said blade, whereby such rotational motion of said blade about said axis will transmit torsional strain to said torsion shaft and be opposed thereby, thus storing energy in said torsion shaft so as to rotate said blade in an opposite direction about said axis to increase the pitch of said blade with a decrease in the thrust exerted thereby.

3. A variable pitch propeller comprising a hub; a blade mounted on said hub for rotation about a radially extending axis, the trailing edge of said blade located on one side of said axis having a greater surface area than the leading edge thereof located on the opposite side of said axis. the thrust exerted by the trailing edge of said blade thus tending to rotate said blade about said axis to decrease the pitch thereof; a hollow main shaft having an after section on which said hub is mounted and a forward engine section, said after section having an annular groove formed in its forwardend and said engine section having a flange formed on its after end; a torsion shaft extending through the after section of said main shaft and having a flange formed on its forward'end; a collar keyed to the forward end of the after section of said main shaft; a

about said' axis to increase the pitch of said blade with a decrease in the thrust exerted thereby.

ROBERT J. RUTHS. HARRY L. DODSON. 

